Birthday Surprise
by Squareline
Summary: Mephisto decides to grant the Okumura brothers their wishes for their 18th birthdays. Well, Rin wanted candy, and Yukio wanted Rin, so why not kill two birds with one stone? YukioXRin
1. Chapter 1

Here goes everything...

WARNING: CONTAINS YAOI. IF THIS OFFENDS YOU, PLEASE HIT THE BACK BUTTON ON YOUR BROWSER, NOW.

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><p>Rin and Yukio exchanged glances, not sure if they heard right.<p>

"Could you kindly repeat what you just said, Mr. Pheles?" Yukio asked, a look of disbelief on his face. Mephisto smirked at the brothers, who sat stiffly on the big purple couch opposite him.

"What's with your reactions? I've been in a Christmas mood lately, so I thought, why not grant my two favorite students their birthday wishes? It makes sense, too. Your birthdays are close to Christmas, right?" Mephisto said, as though him giving out free gifts was a very normal thing. Which it wasn't.

But despite the suspiciousness of it all, Rin was never one to turn down a free gift; especially if it was going to be something that he wanted really badly. So he readily accepted the Headmaster's offer, grinning as he practically skipped out the doors of the office. Yukio, on the other hand, stayed behind and glanced at the demon, who stared back at him from behind his (expensive) cherry mahogany table.

"What are you planning, Sir?" Yukio asked. Mephisto pretended to look hurt.

"Are you doubting me, your wonderfully generous Headmaster?" He said dramatically, but then burst into a sly grin. "Worry not, Okumura-sensei. All I wish for is to grant wishes this Christmas. It is also a very special year, after all." Yukio merely narrowed his eyes in suspicion and bowed before leaving the office.

As the door closed behind Yukio, Mephisto smirked, undoing his illusion. He stroked the Leaper, which had been settled comfortably on his table all this while, and using his own demonic telepathy to look into the Leaper's mind, he grinned. "Well, my dear brothers, let us see what your hearts desire…"

—

Christmas swung by quickly, approximately a week after Mephisto had called his half-brothers to his office. Yukio was still wary of the purple-haired demon and his promised birthday presents, but Rin had been looking forward to his gift ever since then. That was why, after the Christmas/birthday party held at the old boy's dorms, Rin followed Mephisto to his office eagerly to collect his and Yukio's gifts while Yukio stayed behind to clean up with the other cram school students.

Once the cleaning up was done, and the crowd gone, Yukio went back to his room and flopped onto the bed. He glanced over at the clock on his bedside drawer, tensing and jumping out of bed when he saw the time.

"It's already this late? Where's Rin?" He asked aloud, but no one except a drunk, out-cold Kuro was there to hear him. His blood started to boil when he thought of Mephisto. "He'd better not be doing anything weird to Nii-san…" He trailed off, clamping his mouth shut and shaking his head to clear any indecent thoughts. He then decided to wait slightly longer, and then storm into Mephisto's office later if Rin didn't come back anytime soon.

Of course, he wasn't expecting what happened next.

A loud thump against the door was followed by a muffled voice which he recognized to be Rin's. Relieved but concerned, Yukio darted over to the door and opened it, only to have his brother's limp body fall onto him.

"Nii-san? Hey, get a hold of yourself!" Yukio lifted Rin off him, and laid his older brother on the floor. He was panting heavily, his eyes squeezed shut and his face flushed. "Are you okay? What happened?" Yukio asked, worry evident in his voice, but when he touched Rin's forehead, the latter jerked away, whimpered and let out a very erotic moan. Yukio's eyes widened and he quickly pulled his hand back, a blush starting to form on his face. "Nii… san…?"

"Ngh… Yu… Yukio…" Rin groaned, an eye cracking open to look up at his younger brother, who just looked at him with a concerned face.

"What on earth happened, Rin?" Yukio asked, not sure if he should bring Rin over to his bed. He was a Doctor, but he doubted that he could control himself if Rin made any lewd noises. It was _Rin_, after all… Said boy merely writhed on the floor, trying to curl up on his side but cringing as though every small movement was hurting him in some way. "Rin!"

"Stupid… clown… He said… it was… candy…" he murmured breathily. Yukio frowned, and decided to help Rin to his bed before checking if he had anything to counter whatever drug Mephisto had given his brother. He slung Rin's arm over his shoulder and dragged him over to the bed, trying his hardest to stay professional and ignore the temptation of jumping the other boy.

Setting Rin down onto the bed slowly, he decided to leave the checking of symptoms for later and prepare the medicinal kit, hoping that by stalling for time he would be able to calm his raging hormones. Rin whimpered loudly, and Yukio turned around in time to see Rin weakly trying to pry his clothes off his body. "Hot… It's so hot… Yukio…"

"It could be a fever… Nii-san, hang in there. I'm gonna go get some water to sponge you down," he replied, grabbing a towel and running out of the room, into the empty hallways, away from a very, _very_ erotic Rin…

_'Snap out of it, Okumura Yukio!' _he thought as he ran to the sinks, mentally kicking himself for thinking about his brother that way. Sure, he'd always had much admiration for his brother, and it was true that there was a time when he _might_ have developed a _tiny_ crush on him…

'_That was years ago. You're 18 now, Yukio, you should know how to keep your cool and act like a proper 18-year-old.' _He grabbed a small basin from next to the tap, and filled it with cold water. _'It's about time to leave behind those childish feelings and face reality. You're brothers, you're both men…' _Yukio turned off the tap and, throwing the towel into the cold water, made his way back to his room as quickly as possible without spilling any water. '_It's the ultimate sin. Not to mention, we're both already legal adults…' _That last thought did not end as expected for Yukio, and he dipped a hand in the cold water and splashed it on his face to clear his thoughts.

"Nii-san, I'm back," Yukio kicked the half-open door, entering the room and glancing over at Rin, who'd already stripped himself of his shirt. Yukio swallowed and worked quickly, setting down the basin and wringing the towel of excess water. He turned back to his brother and was ready to help sponge him down, but he did not expect a whining Rin to slip onto his lap and wrap his arms around his neck. "N-Rin…?"

"Yukio, please… help me out…" Rin panted, burying his face into his shoulder and weakly grasping Yukio's shirt. The younger's arms hung limp at his side, and he wondered if he should wrap them around Rin, who had pressed his body against Yukio's. The latter felt something hard brush against his thigh and blushed, flinching slightly, his thigh jerking upwards and the friction causing Rin to moan loudly.

"Nii-san…" Yukio gulped, and leaned away from his older brother, whose facial expression was making it hard for him to say no. _'Just this once… '_ The bespectacled teen finally succumbed to his desires, and hesitantly placed his lips on Rin's. He was answered with a hungry growl as Rin responded fiercely, already biting on Yukio's lip. The younger twin smirked and opened his mouth, only to force his tongue into his older brother's. He wasn't going to be easily dominated.

Rin didn't care much about dominance, though, and it seemed as though all he wanted was more; more kissing, more touching, more of that delicious friction against his groin… Yukio didn't mind it at all, and soon found himself sporting a matching erection. "Yukio…" Rin's voice was muffled against his twin's lips, which had now moved down to his neck and was leaving a wet trail of bites and kisses.

"Hold on, Nii-san," Yukio exhaled, and lifted Rin up so that he could move the both of them over to the bed. He removed his glasses, pushed Rin down onto the mattress, and his older brother watched with lustful, half lidded eyes as he stripped himself of his own yellow T-shirt.

"Yukio…" the half-demon moaned as his twin went back to attacking his collar bone, his back arching off the bed when Yukio bit down on a particularly sensitive spot. Yukio smirked against Rin's flushed, sweaty skin and nibbled on that spot, sucking slightly. He pulled away to see a lovely red mark.

"You're mine, Nii-san…" Yukio breathed, and went on to undo his brother's pants, as well as his own. Seeing a mewling Rin in only his boxers with an obvious tent in front was sinfully erotic, and Yukio tore at them, unable to control his lust. Rin gasped as the cool air met his warm skin, back arching off the bed once more as Yukio's hands roamed over every inch of his now exposed body.

"Agh, God… Yuki-!" Rin cried as a hand wrapped around his painfully erect manhood. Yukio could only smirk.

"You're already so wet, Nii-san…" He rubbed a thumb over the tip of Rin's member, and finding his reactions and whimpers extremely addictive, immediately set to work on eliciting more of those sounds and actions from his older brother. Yukio slid down Rin's body so that he faced his erection, and tentatively took it into his mouth. Engulfed by the hot, wet cavern that was Yukio's mouth, Rin couldn't help the long, loud moan that escaped from him.

"Nn, Yukio!" He panted, as Yukio slid his tongue over and around the head of Rin's penis. He then started to lick along its length, stroking it as the elder came into his mouth with a groan. Yukio used his hand to wipe away some of the cum that had landed on his face, and then proceeded to kiss his older brother, who shuddered when he tasted his own seed on the other's tongue.

"Had enough, Rin?" He asked as he pulled away. The other boy growled, pulling him back.

"Hell if I did," he replied, and their mouths smashed together once more. Yukio noticed that Rin was still hard, but his suspicion quickly melted away when the latter ground his hips against him.

"Ah!" Rin yelped when Yukio pushed him down onto the bed once more. When Yukio placed his fingers on his mouth, he gave him a confused look.

"Lick them," Yukio commanded as he removed himself of his own boxers. "I don't want to hurt you too much…" Rin obeyed, and used his saliva to coat Yukio's fingers as thoroughly as possible. Once he thought they were wet enough, Yukio took them out from Rin's mouth and moved them downwards. "Should I continue? There's no turning back after this," he whispered into his brother's ear. Rin just wrapped his arms around Yukio's neck.

"Just hurry up and do it," he panted. Yukio used a finger to circle Rin's hole, lubricating it, and then slid the finger in. Rin squeaked, the intrusion feeling very foreign to him. Yukio paused, afraid that he was causing him pain, but a squeeze on his shoulder from Rin urged him to continue. "It's fine, so… please…"

Yukio nodded, and wiggled his finger around. When he added another finger and started scissoring, Rin couldn't help but cry out in pain. Yukio tried to comfort him by whispering encouraging words into his ear and trying to get him to relax, and once he felt Rin was ready he added a third finger. "Nngh, ah!" Rin cried, but as Yukio's fingers probed inside him, he found himself getting used to it.

"Is it okay now?" Yukio asked, stroking his brother's hair. Rin looked up at him and nodded. Withdrawing his fingers, Yukio positioned himself at Rin's entrance, and slowly pushed himself in. Rin squawked, clutching at the sheets. His cries were silenced when his twin captured his lips, and Rin groaned into Yukio's mouth when the other was fully sheathed in him.

Yukio started a slow pace, and once Rin adjusted he started to go faster, with the other eager to meet his thrusts. The both of them were panting heavily now, Rin emitting the occasional moan while Yukio grunted with each thrust. When the latter changed his angle and rammed upward, brushing against Rin's sweet spot, Rin responded with a strangled moan, louder than those he had been producing until now. Yukio smirked, aiming for that spot with every subsequent thrust, and all Rin could do was gasp and moan, face flushed, eyes squeezed shut in pleasure.

"I'm… close…" The half-demon wailed as he fisted the sheets. Yukio gave a few more hard thrusts and came inside his brother, who followed soon after. Rin's seed splattered over this chest as he arched off the bed, his moans dying on his lips. Yukio smiled and pulled out, flopping onto the other as they continued their heavy breathing.

"_Suki da yo, Yukio…" _ Rin murmured, his eyes closing as he drifted off to sleep. Yukio's eyes widened in surprise, before he smiled in content, pulling his brother into a warm embrace.

"Me too, Nii-san… Happy birthday."

—

Mephisto's eyes gleamed as he set his binoculars down and sipped at his tea. He glanced at the bag of candy that Rin had emptied, and giggled madly as he took out an empty bottle of aphrodisiac pills.

"I hope the both of them enjoyed their presents!"

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><p>Yes, I know it's not their birthday(s) yet. But this was bugging me, so I just had to.<p>

This was my first time writing a lemon, and I won't deny, I was grinning like an idiot while I wrote it... Comments and tips to improve will be greatly appreciated.


	2. Chapter 2: OMAKE

Birthday surprise: OMAKE

Rin groaned as he rolled over, the thin white blanket sliding off his body. Feeling a source of heat nearby, he inched closer and put an arm and a leg around the object, only to feel his limbs being set aside and his body pushed away. He knitted his eyebrows and mumbled something incomprehensible before drifting back to sleep again.

Yukio threw his legs over the side of the bed, sitting up and staring into blank space as he tried to register the fact that it was morning and that he had to prepare for school (and work). Sighing, he got up and walked towards his wardrobe, pausing to frown slightly when he realised that he wasn't wearing any underwear.

"Right, Nii-san and I…" He muttered, casting an anxious glance to the other male who was sleeping peacefully under the sheets.

_'Will he remember what we did? And… how'll he react…?' _Yukio grimaced, imagining the worst possible situation and suddenly feeling very depressed. He picked up the clothes that were carelessly strewn across the floor last night and put them aside, then grabbed a fresh set of clothes and headed towards the showers.

While Yukio went about freshening up for the day, Rin took his own sweet time to wake up, accustom to the bright morning light and sat up slowly, still dazed and sleepy. He then got out of bed, his sleepy expression quickly changing to one of shock.

Rin yelled loudly, and his face flushed as he looked for something to cover up his privates with.

"Wha.. What? Why? How…" He blustered, panicking as he tried to recall what he did last night that caused him to get into this state. He wasn't able to remember anything, though, and he started to enter a state of frenzy.

"Maybe I could ask Yukio," he mumbled, just as the other teen walked into the room with only a towel on, a pile of clothes in his left hand. Usually Rin wouldn't have been embarrassed by the half-naked body of a man, but somehow seeing Yukio's bare torso made him blush and look away.

"And why aren't you wearing clothes, you idiot!" He turned away quickly, causing Yukio to raise an eyebrow.

"I can't put on my clothes if I'm not wearing any underwear, can I? I forgot to bring a clean pair of boxers to the toilet when I was getting my clothes." Yukio explained as he grabbed said underwear and exited the room again, while commenting that the other boy should put on some clothes himself. Rin relaxed slightly, still blushing furiously.

_'What's wrong with me? It's not as if it's my first time seeing Yukio naked. And he had a towel on!' _The half-demon kicked himself mentally, before deciding that he was still half asleep and needed a trip to the sinks to splash cold water on his face. He grabbed a face towel from the rack and a cup with his toothbrush and toothpaste in it, before walking towards the door. He was just a meter away when he stepped into a basin of water, which slid backwards as he fell forward with a loud yelp.

Pain shot up from his abdomen as water rained down on him, and Rin was sure that he was fully awake at this point of time. He growled, rubbing his abused tummy as he sat up and glared at the offending basin. His glaring was cut short when he heard running footsteps and the door slammed open.

"Nii-san, are you alright? I heard… screaming…" Yukio trailed off, his eyes wide as he took in the sight of a naked, wet Rin sitting on the floor with his hand dangerously low on his torso. "… What are you doing, Nii-san?"

The younger brother's face was expressionless, while Rin's face started to heat up at an astonishing rate.

"It's not what it looks like! I swear! I just wanted to go grab some clothes, then this basin appeared out of nowhere, and then I stepped in it and slipped and… Will you stop looking at me, goddammit? This is so embarrassing!" Rin flailed, emphasising his words with elaborate hand gestures while seemingly amused Yukio just watched.

What Rin didn't know was that Yukio was having a hard time holding himself back, and the younger twin just cleared his throat.

"Well, Nii-san, what you do with basins of water isn't any of my business but it's only seven in the morning and I just took a shower, so please try not to turn me on so much," Yukio commented half-jokingly as he packed his bags, smiled and turned to leave for school. Rin just stared at where Yukio used to be standing, as his brain worked to process the other male's words.

"Turn… on? … Ah!" Memories of the previous night flooded his mind in excruciating detail, and his heart started to beat faster, the blood going straight to his face and groin. His eyes wide with realisation and mortification, he backed away from the door and curled into a ball, burying his red face in his knees.

"I can't believe we actually… And I can't believe I actually asked him to…" Rin pouted, crestfallen. Kuro snickered from the windowsill he was lying on.

**"Rin, you didn't ask him. You begged, like a demon dog in heat begging for sex." **The Cat Sith grinned as he stretched lazily, before a basin made contact with his body. Kuro yelped as the impact forced him out of the window and into the bushes below.

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><p><strong>2712/11 Edit:**

Phew, I made it. -breaks down and cries in joy-

Well, this fic's supposed to be a oneshot, but I came up with the idea and posted it waaaay before their actual birthday... So this little Omake's to celebrate the twins' 16th birthday(s?) (even though they're 18 in the story, but meh) Was planning something longer, but it's an omake, so I figured around 900 words should suffice. Anyway, happy birthday Rin and Yukio! 8D

And to everyone, Merry Christmas and a Happy New Year!


End file.
